1. Field of the Invention
This invention relates to a multistage fuel injection system for injecting fuels of different kinds into cylinders of an internal combustion engine such as a marine diesel engine.
2. Prior Art
Japanese Patent Laid-open Publication No. 58-77160 discloses a high pressure fuel injection system in which a controlled amount of fuel is introduced into an intensifier or booster where fuel is increased in pressure by a working fluid supplied to the booster and then it is supplied to an injection nozzle, the supply of working fluid being adjusted by a solenoid valve for automatically controlling the fuel injection timing.
According to another fuel injection system disclosed in Japanese Patent Laid-open Publication No. 50-119130, immediately after the injection of a main fuel such as diesel fuel oil, an auxiliary fuel such as water is injected into engine cylinders so as to completely burn an unburned or excessively thick fuel-and-air mixture, thereby increasing the heat generating efficiency of the cylinders. The main fuel is supplied by a fuel injection pump to a distributor for driving plungers thereof to thereby distribute the main and auxiliary fuels respectively to a pair of main and auxiliary injection nozzles at different timings, thus effecting a multistage fuel injection.
It is easy to obtain a multistage high pressure fuel injection system by combining the teachings of the above-mentioned publications. The resultant fuel injection system is however still unsatisfactory in that since two injection nozzles must be installed in a cylinder head of each cylinder, it is difficult to achieve a proper orientation of such injection nozzles the lack of such a proper orientation would result in an inaccurately controlled fuel injection and a low heat generating efficiency of the engine cylinder.